And, the reverse–which actors have been particularly badly cast in roles of characters you first met in the pages of a book? Do you blame the actors or the writers and other film-people for the failure? Who would you have cast instead?
“Nightmare” is such a strong word, isn’t it? I’d reserve it for something as egregious as whitewashing or anything else flat-out offensive. I’ve seen plenty of actors that I, were I a casting director, perhaps might not have cast as certain characters, but I’ve so rarely seen anyone completely fail at playing a character that I can’t even think of an example. Acting is a job like any other; at the end of the day, every actor wants to do good work for good money. If the character is poorly written, that’s the screenwriters’ fault, not theirs.
This question reminds me a little of the film adaptation of Interview with a Vampire. Anne Rice was livid that Tom Cruise was cast as Lestat. She just couldn’t see any way that Maverick could do her character justice. Then she saw the film. Afterwards, she wrote Cruise a letter of apology. Cruise is, perhaps, not everybody’s vision of Lestat, but the stamp that he does put on the character, emphasizing his weaknesses in a way that makes him entertaining as both a character and an antagonist, is an enjoyable one.
The point is, there’s always plenty of room for different interpretations of literary characters, with, of course, some reasonable exceptions (no, the cast of Anansi Boys can’t be white!). After all, they’re safe and sound in their books.